1. Field of the Invention
The present invention relates to a manual pulling apparatus which is useful also as a hoist and which is driven manually in the same manner as chain blocks for pulling a load chain to draw a package fastening rope or for lifting a heavy article.
2. Description of the Prior Art
With known pulling of hand hoist apparatus, a load sheave driving pinion fixedly mounted on a drive shaft is adapted to be held in meshing engagement with intermediate gears by being pressed on a side portion thereof with a spring. When the pinion is disengaged from the intermediate gears, the load sheave is freely rotatable, whereby a chain can be paid off from the load sheave free of resistance to reach the article to be pulled along. However, to move the pinion axially thereof out of engagement with the intermediate gears, a hand wheel fixedly mounted on the drive shaft must be pulled toward the user with a considerably great force against the action of the spring. See, for example, Japanese Pat. No. 728,097.
Thus, with the known hoist apparatus described, the load sheave driving pinion is held in meshing engagement with the intermediate gears only by the pressing force of the spring. Accordingly when the spring becomes fatigued or the intermediate gears are worn, the drive shaft tends to retract while the pinion is in rotation, with the resulting likelihood that the pinion will disengage from the intermediate gears.
The conventional hoist apparatus of the type described further has a ratchet wheel provided between the friction plates of a brake assembly and a reverse rotation preventing pawl engaging the ratchet wheel and supported by a pin on one of the side plates for holding the load sheave. Consequently when the load sheave is heavily loaded, the opposed side plates are likely to deform inward toward each other at their center portions where the side plates are not connected together by stay bolts to maintain a specified distance therebetween. The deformation of the side plates will alter the posture of the pin projecting from one of the side plates and also the posture of the reverse rotation preventing pawl which is mounted on the pin so as to act on the ratchet wheel. The pawl is then liable to disengage from the ratchet wheel.